The present invention generally provides devices, systems, methods, and kits for labeling and/or tracking inventories of elements. In a particular embodiment, the invention provides improved identification systems and methods which make use of labels that emit differentiable spectra, the spectra preferably including a number of signals having measurable wavelength maxima, minima, and/or intensities.
Tracking the locations and/or identities of a large number of items can be challenging in many settings. Barcode technology in general, and the Universal Product Code in particular, has provided huge benefits for tracking a variety of objects. Barcode technologies often use a linear array of elements printed either directly on an object or on labels which may be affixed to the object. These barcode elements often comprise bars and spaces, with the bars having varying widths to represent strings of binary ones, and the spaces between the bars having varying widths to represent strings of binary zeros.
Barcodes can be detected optically using devices such as scanning laser beams or handheld wands. Similar barcode schemes can be implemented in magnetic media. The scanning systems often electro-optically decode the label to determine multiple alphanumerical characters that are intended to be descriptive of (or otherwise identify) the article or its character. These barcodes are often presented in digital form as an input to a data processing system, for example, for use in point-of-sale processing, inventory control, and the like. Barcode techniques such as the Universal Product Code have gained wide acceptance, and a variety of higher density alternatives have been proposed. Unfortunately, these known barcodes are often unsuitable for labeling many “libraries” or groupings of elements. For example, small items such as jewelry or minute electrical components may lack sufficient surface area for convenient attachment of the barcode. Similarly, emerging technologies such as combinatorial chemistry, genomics and proteomics research, microfluidics, micromachines, and other nanoscale technologies do not appear well-suited for supporting known, relatively large-scale barcode labels. In these and other ongoing work, it is often desirable to make use of large numbers of fluids, and identifying and tracking the movements of such fluids using existing barcodes is particularly problematic. While a few chemical encoding systems for chemicals and fluids had been proposed, reliable and accurate labeling of large numbers of small and/or fluid elements remained a challenge.
Small scale and fluid labeling capabilities have recently advanced radically with the suggested application of semiconductor nanocrystals (also known as Quantum Dot particles), as detailed in U.S. patent application Ser. No. 09/397,432, the full disclosure of which is incorporated herein by reference. Semiconductor nanocrystals are microscopic particles having size-dependent electromagnetic signal generation properties. As the band gap energy of such semiconductor nanocrystals vary with a size, coating and/or material of the crystal, populations of these crystals can be produced having a variety of spectral emission characteristics. Furthermore, the intensity of the emission of a particular wavelength can be varied, thereby enabling the use of binary or higher order encoding schemes. A label generated by combining semiconductor nanocrystals having differing emission signals can be identified from the characteristics of the spectrum emitted by the label when the semiconductor nanocrystals are energized.
While semiconductor nanocrystal-based inventory control schemes represent a significant advancement for tracking and identifying many elements of interest, still further improvements would be desirable. In general, it would be desirable to provide improved identification systems, methods for identifying elements, and/or identifiable groups or libraries of elements. It would be particularly beneficial if these improved inventory and identification systems enhanced the accuracy, reliability and robustness of the identifications provided by the system. Ideally, these improvements should allow enhanced differentiation of the labeled elements without significantly increasing the overall costs, complexity and/or size of the labels and associated system components. At least some of these objectives may be provided by the inventions described hereinbelow.